On the other hand, while fully alive to the undesirability, and indeed wickedness, of putting ideas of dread and suffering into children's minds unnecessarily, yet so much of the misery in the world is due to ignorance, and could have been avoided if knowledge of the simplest character had been given at the proper time, that it has been thought best to set forth the facts as to the causation and nature of the commonest diseases, and the methods by which they may be avoided. This is peculiarly necessary from the fact that most of the gravest enemies of mankind have come into existence within a comparatively recent period of the history of life,--only since the beginning of civilization, in fact,--so that we have as yet developed no natural instincts for their avoidance. Nor do we admit that we are adding anything to the stock of fears in the minds of children--the nurse-maid and the bad boys in the next alley have been ahead of us in this respect. The child-mind is too often already filled with fears and superstitions of every sort, passed down from antiquity. Modern sanitarians have been accused of merely substituting one fear for another in the mind of the child--bacilli instead of bogies. But, even if this be true, there are profound and practical differences between the two terrors. One is real, and the other imaginary. A child cannot avoid meeting a bacillus; he will never actually make the acquaintance of a bogie. Children, like savages and ignorant adults, believe and invent and retail among themselves the most extraordinary and grotesque theories about the structure and functions of their bodies, the nature and causation of their illnesses and aches and pains. A plain and straightforward statement of the actual facts about these things not only will not shock or repel them, or make them old before their time, but, on the contrary, will interest them greatly, relieve their minds of many unfounded dreads, and save them from the commonest and most hurtful mistakes of humanity--those that are committed through ignorance. THE AUTHOR. CONTENTS PAGE I. RUNNING THE HUMAN AUTOMOBILE 1 II. WHY WE HAVE A STOMACH 4 What Keeps Us Alive 4 The Digestive System 7 The Journey down the Food Tube 9 III. THE FOOD-FUEL OF THE BODY-ENGINE 21 What Kind of Food should We Eat? 21 The Three Great Classes of Food-Fuel 25 IV. THE COAL FOODS 27 Proteins, or "Meats" 27